Adsorption cooling/conditioning systems (ACCS) are already known as such. Open thermochemical systems based on adsorption/ desorption of water are particularly advantageous. In this case, an adsorbent capable of binding water is used as the working medium. Typical adsorbents for thermochemical systems, which have been investigated so far, are salts such as lithium chloride or calcium chloride, acids such as sulfuric acid or phosphoric acid, or adsorbents based on silica and/or alumina, in particular silica gel, or silicates such as synthetic or natural zeolites.
The adsorbents used in the past have a number of disadvantages. Solid adsorbents such as, for example, zeolites are usually suitable only as "fixed working media" and therefore permit only a discontinuous procedure with respect to adsorption and regeneration or, if they are to be used as a "circulating working medium" in a continuous regeneration process, must meet special requirements with respect to form (preferably spherical), bulk density and abrasion resistance, because transportation of the adsorbent is then necessary, for example pneumatic transportation. By contrast, liquid working media can be pumped and are therefore advantageous. For use of such liquid working media in adsorption cooling/conditioning, however, high concentrations of dissolved salt in the working media are necessary. But high salt concentrations increase the tendency to salt precipitation, restrict the method of operation and reduce the reliability in use. There is a risk of the working medium solidifying, particularly at such sites of use which require air conditioning during the day and in the evening, but where the night temperatures can fall below, for example, 20.degree. C. Solidification of the working medium would render the air-conditioning unit unusable for a prolonged period of time.
There is therefore the problem of combining a high salt concentration with a low precipitation temperature of the salt from the solution. Suitable working media should have low water vapor partial pressures at ambient temperature (adsorption process) and high partial pressures at slightly elevated temperatures (60.degree. to 80.degree. C.; desorption process, regeneration) and should be composed of inexpensive components which, as far as possible, are compatible with the environment.